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A GROUP BY statement in SQL specifies that a SQL SELECT statement partitions result rows into groups, based on their values in one or several columns. Typically, grouping is used to apply some sort of aggregate function for each group. [ 1][ 2] The result of a query using a GROUP BY statement contains one row for each group.
Aggregate function. In database management, an aggregate function or aggregation function is a function where multiple values are processed together to form a single summary statistic . (Figure 1) Entity relationship diagram representation of aggregation. Common aggregate functions include: Average (i.e., arithmetic mean) Count. Maximum. Median.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
SQL:1999 (also called SQL 3) was the fourth revision of the SQL database query language. ... GROUP BY was extended with ROLLUP, CUBE, and GROUPING SETS.
WHERE is taken into account at an earlier stage of a query execution, filtering the rows read from the tables. If a query contains GROUP BY, rows from the tables are grouped and aggregated. After the aggregating operation, HAVING is applied, filtering out the rows that don't match the specified conditions. Therefore, WHERE applies to data read ...
Select (SQL) The SQL SELECT statement returns a result set of rows, from one or more tables. [1] [2] A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language ...
ORDER BY is the only way to sort the rows in the result set. Without this clause, the relational database system may return the rows in any order. If an ordering is required, the ORDER BY must be provided in the SELECT statement sent by the application. Although some database systems allow the specification of an ORDER BY clause in subqueries ...
SQL syntax. The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.